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[skip-ci] [io] Collapse data format details of TFile class #14929

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Apr 4, 2024
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[skip-ci] [io] Collapse data format details of TFile class #14929

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[skip-ci] [io] Collapse data format details of TFile class.
ferdymercury Mar 11, 2024
a7045f5
[skip-ci] cross-reference markdown docu with link as well as human-re…
ferdymercury Mar 11, 2024
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10 changes: 10 additions & 0 deletions io/io/src/TFile.cxx
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Original file line number Diff line number Diff line change
Expand Up @@ -13,6 +13,12 @@
\file TFile.cxx
\class TFile
\ingroup IO
\brief A ROOT file is an on-disk file, usually with extension .root, that stores objects in a file-system-like logical structure, possibly including subdirectory hierarchies.
\sa \ref IO
\sa \ref rootio (or `io/doc/TFile` folder in your codebase)

<details>
<summary>ROOT file data format specification</summary>

A ROOT file is composed of a header, followed by consecutive data records
(`TKey` instances) with a well defined format.
Expand All @@ -21,6 +27,7 @@ The first data record starts at byte fBEGIN (currently set to kBEGIN).
Bytes 1->kBEGIN contain the file description, when fVersion >= 1000000
it is a large file (> 2 GB) and the offsets will be 8 bytes long and
fUnits will be set to 8:

Byte Range | Record Name | Description
----------------|-------------|------------
1->4 | "root" | Root file identifier
Expand Down Expand Up @@ -69,7 +76,10 @@ Byte Range | Member Name | Description
Begin_Macro
../../../tutorials/io/file.C
End_Macro

The structure of a directory is shown in TDirectoryFile::TDirectoryFile

</details>
*/

#include <ROOT/RConfig.hxx>
Expand Down